At the moment, bandwidth tokens in Tribler do not represent any monetary value and they are not a form of digital cash. They act as an indicator of how much you contributed to and consumed from the network (although the name ‘token’ can be confusing, we already had internal discussions about that). If you use the services of relay/exit nodes when downloading anonymously, the amount of tokens you have will decrease whereas acting as a relay node will increase your balance. All contributions and consumptions are recorded on a distributed ledger, resulting in a large graph with interactions. Eventually we might integrate a mechanism where one can sell these interactions to other users for cryptocurrencies, e.g., Bitcoin. If you are interested in this line of work, you can find more information in this write-up.